Prostatic tissues subjected to different therapeutic modalities are being studied for potential predictors for treatment selection and response. Two models are presently under investigation: (1) Prostatic tumor tissue serially transferred in nude mice, and (2) a prostatic adenocarcinoma cell line (DU 145) and short term tissue cultures. The tissue culture system is used to design a useful in vitro assay for screening chemotherapeutic drug effectiveness. Measurement of drug effectiveness is done by determination of inhibition of incorporation of radioactively labeled precursors to DNA, RNA and proteins. The assay, as designed, uses a minimal amount of tissue and will provide drug sensitivity data for individual tumor tissues within one week. This in vitro sensitivity profile will be compared with clinical data on patients undergoing chemotherapy. For studies on radiation therapy the nude mouse system is used. Large amounts of homogeneous human tumor material can be acquired by transfers in nude mice. We have established conditions which allow to locally apply patient doses to tumors growing in nude mice. We are now ready to study morphological changes which occur after radiation of tumors and to establish dose response curves for tumors of different origin.